Air-conditioning control unit

ABSTRACT

An air-conditioning control unit ( 26 ) controls the airflow distributing door ( 16 ), a first indoor heat exchanger ( 10 ) is provided in the first air passage ( 21 ) and a second indoor heat exchanger ( 4 ) is provided in the second air passage ( 22 ). in adjusting air sent from the first air passage ( 21 ) is distributed into the second air passage ( 22 ) and the third air passage ( 23 ) by controlling the airflow distributing door ( 16 ). In switching from the cooling operation state to the heating operation state, the flow of the adjusting air in the second air passage ( 22 ) is increased by controlling the airflow distributing door ( 16 ) by the air-conditioning control unit ( 26 ) prior to the switching of refrigerant circuit from the cooling control mode to the heating control mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioning control unit usedfor an air conditioning system that performs heating operation using arefrigerant of a fuel car, electric car or the like as a heat source.

2. Description of the Related Art

A Well-known conventional air conditioning system adjusts temperature ofair in a cabin by mixing hot air from a heat exchanger of a radiator foran engine as a heat source and cold air from a cooler using refrigerantas disclosed in a patent brochure, Japanese Patent Application Laid-OpenNo. 2002-274147.

In the case where cooling water in the radiator for the engine is usedas a beat source, the above described conventional air conditioningsystem would be effective to control the temperature of air in thecabin.

However, in the case where no heat source of the engine exists, as inthe electric vehicle by fuel cell, since the air conditioning system isrequired another heat source, structure and control of the systembecomes complex and manufacturing cost thereof is raised.

SUMMARY OF THE INVENTION

The present invention has been achieved with such points in mind.

It therefore is an object of the present invention to provide aair-conditioning control unit used in a air conditioning system wheretemperature of the air in the cabin of vehicle can be more accuratelycontrolled, and manufacturing cost thereof can be reduced.

To achieve the object, according to a first aspect of the presentinvention, there is provided an air-conditioning control unit (26) usedin a air conditioning system (1) which comprises: a refrigerant circuit(2); a first indoor heat exchanger (10) having a low refrigeranttemperature; a second indoor heat exchanger (4) having a highrefrigerant temperature; controlled components (5, 12); a first airpassage (21); and a second air passage (22) and a third air passage (23)which are distributed by an airflow distributing door (16) from thefirst air passage (21), wherein the air-conditioning control unit (26)controls the controlled components (5, 12) and the airflow distributingdoor (16); wherein the first indoor heat exchanger (10) is provided inthe first air passage (21); wherein the second indoor heat exchanger (4)is provided in the second air passage (22); wherein adjusting air sentfrom the first air passage (21) is distributed into the second airpassage (22) and the third air passage (23) by controlling the airflowdistributing door (16); wherein switching is carried out between an airflowing state during heating in which air is distributed mainly into thesecond air passage (22) and an air flowing state during cooling in whichair is distributed mainly into the third air passage (23); whereinswitching between a cooling operation state and a heating operationstate is carried out by controlling the controlled components (5, 12)and thereby performing switching between a cooling control mode and aheating control mode in the refrigerant circuit (2); and wherein, inswitching from the cooling operation state to the heating operationstate, the flow of the adjusting air in the second air passage (22) isincreased by controlling the airflow distributing door (16) by theair-conditioning control unit (26) prior to the switching of refrigerantcircuit from the cooling control mode to the heating control mode.

In the structure according to the first aspect of the present invention,when cooling operation is switched to heating operation, the airflowdistributing door (16) is controlled so as to increase the quantity ofadjusting air flowing into the second air passage (22) prior toswitching of the refrigerant circuit from the cooling control mode tothe heating control mode. As a result, since high-temperature airstagnating during cooling operation is discharged, the temperature ofthe adjusting air can be detected more accurately by the air temperaturesensor (25) provided at the downstream of the second indoor heatexchanger (4).

According to a second aspect of the present invention, as it dependsfrom the first aspect, there is provided an air-conditioning controlunit (26) wherein the airflow distributing door (16) is controlled so asto flow smaller quantity of adjusting air into the second air passage(22) than the air flowing into the third air passage (23) in the airflowing state during cooling.

In the structure according to the second aspect of the presentinvention, since the airflow distributing door (16) is controlled sothat smaller quantity of adjusting air flows into the second air passage(22) than the air flowing into the third air passage (23) during coolingoperation, rapid change in temperature of the adjusting air can besuppressed.

According to a third aspect of the present invention, as it depends fromthe first or the second aspect, there is provided an air-conditioningcontrol unit (26) wherein the airflow distributing door (16) iscontrolled so as to flow smaller quantity of adjusting air into thethird air passage (23) than the air flowing into the second air passage(22) in the air flowing state during heating.

In the structure according to the third aspect of the present invention,since the airflow distributing door (16) is controlled so that smallerquantity of adjusting air flows into the third air passage (23) than theair flowing into the second air passage (22) during heating operation,rapid change in temperature of the adjusting air can be suppressed.

According to a fourth aspect of the present invention, as it dependsfrom one aspect among the first to the third aspect, there is providedan air-conditioning control unit (26) wherein the second air passage(22) is connected to an air outlet on the lower side in the room and thethird air passage (23) is connected to an air outlet on the upper sidein the room.

In the structure according to the fourth aspect of the presentinvention, since the second air passage (22) is connected to the airoutlet on the lower side in the room and the third air passage (23) isconnected to the air outlet on the upper side in the room, the upperside in the room can be maintained at relatively low temperatures,improving comfortability during heating operation.

According to a fifth aspect of the present invention, as it depends fromone aspect among the first to the fourth aspect, there is provided anair-conditioning control unit (26) wherein position of the airflowdistributing door (16) is changed so as to decrease a difference betweenblowing temperature of the adjusting air and control target temperature.

In the structure according to the fifth aspect of the present invention,the position of the airflow distributing door (16) is changed so as todecrease a difference between the blowing temperature of adjusting airand the control target temperature, rapid change in temperature of theadjusting air can be suppressed.

BRIEF DESCRIPTION OF THE ACCOMPANYNG DRAWINGS

FIGS, 1A and 1B are views showing position of an airflow distributiondoor of an air conditioning system during cooling operation (FIG. 1A)and heating operation (FIG. 1B) in accordance with the embodiment of thepresent invention,

FIG. 2 is a view showing an improved air conditioning system comprisingan air-conditioning control unit in accordance with an embodiment of thepresent invention (cooling operation state).

FIG. 3 is a view showing an improved air conditioning system comprisingan air-conditioning control unit in accordance with the embodiment ofthe present invention (heating operation state).

FIG. 4 is a flowchart showing an example of a control procedure of theair-conditioning control unit in accordance with the embodiment of thepresent invention.

FIG. 5 is a flowchart showing an example of a control procedure of theair-conditioning control unit in accordance with the embodiment of thepresent invention (continued from FIG. 4).

FIG. 6 is a flowchart showing an example of a control procedure of theair-conditioning control unit in accordance with the embodiment of thepresent invention (continued from FIGS. 4 and 5).

FIG. 7 is a view showing a control example of the airflow distributiondoor in accordance with the embodiment of the present invention in thecooling operation state.

FIG. 8 is a view showing a control example of the airflow distributiondoor in accordance with the embodiment of the present invention in theheating operation state.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There will be detailed below the preferred embodiments of the presentinvention with reference to the accompanying drawings. Like members aredesignated by like reference characters.

FIGS. 1A and 1B show a first embodiment of the present invention. Thedrawings show an arrangement of a first air passage 21 which are dividedby a wall into a second air passage 22 and a third air passage 23 in aduct 20. There is provided with a first indoor heat exchanger 10 in thefirst air passage 21, and with a second indoor heat exchanger 4 in thesecond air passage 22. Furthermore, at the end of the wall which islocated between the second air passage 22 and the third air passage 23,there is provided with a airflow distribution door 16 which is swunglycontrolled by an air-conditioning unit 26 according to the presentinvention.

In the above described arrangement shown in FIGS. 1A and 1B, air passesthrough the first indoor heat exchanger 10 (at low temperate) andairflow flowing into the second indoor heat exchanger 4 (at hightemperature) are mixed or adjusted at an appropriate ratio by theairflow distributing door 16 so as to adjust temperature of the airwhich blow into the cabin of the vehicle or car.

In this case, as shown in the state shown in FIG. 1A for during coolingoperation, control is carried out by using an air temperature sensor 24which is located at the downstream end of the first indoor heatexchanger 10. Further, during cooling operation, for the improvement ofefficiency, cooling level is adjusted by controlling the number ofrevolutions of a compressor and basically, no air is flown to the sideof the second indoor heat exchanger 4. For this reason, high-temperatureair may stagnate in the vicinity of the second indoor heat exchanger 4during cooling operation.

In addition to the above arrangement, another air temperature sensor 25is located at the downstream end of the second indoor heat exchanger 4.When heating operation mode (as shown in FIG. 1A) is carried out rightafter cooling operation mode (as shown in FIG. 1B), since control iscarried out based on the temperature detected by an air temperaturesensor 25 immediately since switching from the cooling operation mode tothe heating operation mode, it is wrongly determined that air in thesecond air passage is sufficiently heated although not sufficientlyheated in fact. This may lead to inadequate control.

A second embodiment of the air conditioning system 1 including theair-conditioning control unit 26 will be described hereinbelow withreferring to the accompanying drawings, FIG. 2 to FIG. 8. The secondembodiment is improved in such point described in the former paragraph.

FIGS. 2 and 3 show the air conditioning system 1 having theair-conditioning unit 26 according to the present invention. Especially,FIG. 2 shows the cooling operation mode and FIG. 3 shows the heatingoperation mode.

As shown in FIG. 2, in the cooling operation mode, a compressor 3, thesecond indoor heat exchanger 4, the outdoor heat exchanger 6, aninternal heat exchanger 8, an expansion valve 9, the first indoor heatexchanger 10, an accumulator 11 and an internal heat exchanger 8 areconnected to each other by piping in this order and a refrigerantcirculates in the direction of arrows (first refrigerant cycle 2 c).

The compressor 3 is disposed, for example, at the outside of thevehicle, compresses a sucked low-pressure refrigerant and discharges thecompressed high-temperature and high-pressure refrigerant. Thecompressor 3 is, for example, an electric compressor driven by electricpower.

The outdoor heat exchanger 6 is disposed at the outside of the car andexposed to outside air by driving a blowing means (not shown) such as anelectric fan. The outdoor heat exchanger 6 radiates heat of therefrigerant to the outside air by exchanging heat between thehigh-temperature and high-pressure refrigerant passing theretrough andthe outside air.

The expansion valve 9 reduces the pressure of the refrigerant, the heatof which is radiated in the outdoor beat exchanger 6.

The first indoor heat exchanger 10 is disposed in the car and air issent into the car through the first indoor heat exchanger 10 by drivinga blowing means (not shown) such as a blower fan. The first indoor heatexchanger 10 extracts heat from air flowing in the car and cools the airby exchanging heat between the low-temperature and low-pressurerefrigerant and the blown air.

The internal heat exchanger 8 allows heat to be exchanged between thehigh-pressure refrigerant, the heat of which is radiated in the outdoorheat exchanger 6, and the low-pressure refrigerant, the heat of which isabsorbed in the first indoor heat exchanger 10.

The accumulator 11 separates the refrigerant from the first indoor heatexchanger 10 into the liquid one and the gaseous one, sends only thegaseous refrigerant and stores the liquid refrigerant temporarily.

On the other hand, as shown in FIG. 3, in the heating operation mode,the compressor 3, the second indoor heat exchanger 4, the internal heatexchanger 8, the expansion valve 15, the outdoor heat exchanger 6, theaccumulator 11 and the internal heat exchanger 8 are connected to eachother by piping in this order and the refrigerant circulates in thedirection of arrows (second refrigerant cycle 2 h).

The second indoor heat exchanger 4 is disposed in the car and air issent into the car through the second indoor heat exchanger 4 by drivinga blowing means (not shown) such as a blower fan. The second indoor heatexchanger 4 heats the air flowing in the car and radiates heat of therefrigerant by exchanging heat between the high-temperature andhigh-pressure refrigerant passing therethrough and the blown air.

The expansion valve 15 reduces the pressure of the refrigerant, the heatof which is radiated in the second indoor heat exchanger 4.

The outdoor heat exchanger 6 is disposed at the outside of the car andexposed to outside air by driving a blowing means (not shown) such as anelectric fan. The outdoor heat exchanger 6 allows the refrigerant toabsorb heat by exchanging heat between the low-temperature andlow-pressure refrigerant passing therethrough and the outside air.

In the case where the same operations are carried out both in thecooling operation mode and heating operation mode, description thereofwill be omitted.

Reference numeral 5 designates a three-way valve, and reference numeral12 designates a solenoid valve. The three-way valve 5 and the solenoidvalve 12 are collectively constituted as controlled component 5, 12which are controlled by the air-conditioning control unit 26. Referencenumerals 7, 13 and 14 designate a check valve.

An air-conditioning control unit 26 consisting of a microcomputercontrols the expansion valves 9, 15, the three-way valve 5, the solenoidvalve 12, (a drive mechanism of) an airflow distribution door 16 andother equipment based on detected values of various sensors (an airtemperature sensor 24 and the like) or input information of anoperational panel (not shown) and the like. Among them, the three-wayvalve 5 and the solenoid valve 12 are controlled components relating tothe switching of the refrigerant cycles.

The air cooled in the first indoor heat exchanger 10 is distributed intoa second air passage 22 passing through the second indoor heat exchanger4 and another third air passage 23 bypassing the second indoor heatexchanger 4 at an appropriate ratio by the airflow distribution door 16.In the case where a cooling and heating efficiency is maximized,however, the airflow distribution door 16 is controlled so as topositioned to block the second air passage 22 in the cooling operationstate (hereinafter referred to as F/COOL) (FIG. 2) and to block thethird air passage 23 in the heating operation state (hereinafterreferred to as F/HOT) (FIG. 3). The air passing through the second airpassage 22 and the air passing through the third air passage 23 aremixed in an air mix chamber (not shown) and blown out from an air outlet(not shown) toward the inside of the car.

Next, an example of control procedures of the airflow distribution doorby the air-conditioning control unit in accordance with this embodimentwill be described with reference to FIGS. 4 to 8. FIGS. 4 to 6 areflowcharts of the control procedures, FIG. 7 is a view showing an airpassage running certain quantity of regulating air at the side of thesecond air passage in the cooling operation state and FIG. 8 is a viewshowing an air passage running certain quantity of regulating air at theside of the third air passage in the heating operation state. In FIGS. 4to 6, the airflow distribution door 16 is referred to as A/MIX.

Firstly, at a step S10, the air-conditioning control unit 26 determineswhether or not a time interval Ti has passed after previous control.When Ti has passed, the procedure of determining a control targetposition of the airflow distribution door 16 is carried out and when Tihas not passed, the procedure of controlling the airflow distributiondoor 16 at the control target position is carried out (FIG. 6).Preferably, this Ti is determined depending on rate of change of roomair temperature. It is set to be six seconds, for example.

At a step S11, in the case of heating control mode, the air-conditioningcontrol unit 26 carries out procedures of changing the control targetposition of the airflow distribution door 16 depending on an air outletmode, position of the airflow distribution door 16 and a differencebetween a blowing temperature and a control target temperature (stepsS12 to S19; FIG. 4). At a step S20, in the case of cooling control mode,the air-conditioning control unit 26 carries out procedures of changingthe control target position of the airflow distribution door 16depending on the number of revolutions of the compressor 3, position ofthe airflow distribution door 16 and a difference between a blowingtemperature and a control target temperature (steps S21 to S29; FIG. 5).At a step S20, in the case where the mode is neither heating controlmode nor cooling control mode, the air-conditioning control unit 26carries out procedures of driving and controlling the airflowdistribution door 16 at the control target position (steps S30 to S32;FIG. 6).

In the heating control mode, at a step S12, it is determined whether ornot the air outlet mode is set at bi-level (described as B/L in thefigure). The bi-level is the state where the third air passage 23 isconnected to the air outlet on the upper side in the room and the secondair passage 22 is the air outlet on the lower side in the room. When theair outlet mode is not set at bi-level, the target position of theairflow distribution door 16 is set at F/HOT (see FIG. 3) (step S13).

When the air outlet mode is set at bi-level, at a step S14, it isdetermined whether or not the airflow distribution door 16 is locatedcloser to the F/COOL side than a second specified position (see FIG. 2).When the airflow distribution door 16 is located closer to the F/COOLside than a second specified position, the control target position isdefined as the second specified position.

Here, as shown in FIG. 8, the second specified position is a position atwhich small quantity of adjusting air is distributed into the third airpassage 23. When the airflow distribution door 16 is located at thesecond specified position, smaller quantity of adjusting air flows intothe third air passage 23 than the air-flowing into the second airpassage 22. In this state, since both of warm air and cool air are blowninto the room, such control is effective especially when rapid change intemperature of the adjusting air is undesirable, for example, atswitching from heating to cooling. Further, in this embodiment, theairflow distribution door 16 is located at the second specified positionin the state where the air outlet mode is set at bi-level. This leads toan advantage of improving comfortability since cool air is blown to theupper side in the room and heat air is blown to the lower side in theroom.

When the airflow distribution door 16 is not located closer to theF/COOL side than the second specified position at a step S14, anabsolute value of temperature difference between the blowing temperatureand the control target temperature is compared with a predeterminedthreshold value and it is determined whether or not the blowingtemperature is much lower than the control target temperature at a stepS16. Subsequently, when the blowing temperature is much lower than thecontrol target temperature, the control target position of the airflowdistribution door 16 is shifted toward the F/HOT side (step S17).

At a step S18, an absolute value of temperature difference between theblowing temperature and the control target temperature is compared witha predetermined threshold value and it is determined whether or not theblowing temperature is much higher than the control target temperatureat a step S18. Subsequently, when the blowing temperature is much higherthan the control target temperature, the control target position of theairflow distribution door 16 is shifted toward the F/COOL side (stepS19). Preferably, the shift of the control target position in the stepsS17 and S19 is performed in increments of a predetermined relativelyminute angle (for example, an angle obtained by dividing an anglebetween the F/COOL and F/HOT positions by 125).

Such control has an advantage of suppressing rapid change in temperatureof the adjusting air. As described herein, in terms of heatingefficiency, it is advantageous that control is carried out so as toreduce the temperature difference only when the temperature differencebetween the blowing temperature and the control target temperature islarge.

On the other hand, in the cooling control mode, at a step S21, it isdetermined whether or not the number of revolutions of the compressor 3equals a threshold number of revolutions Nth or more. The thresholdnumber of revolutions Nth is set to be close to the minimum number ofrevolutions of the compressor 3 in the state where heating operation isswitched to cooling operation and vice versa. For example, when thenumber of revolutions of the compressor 3 ranges from 30 Hz to 120 Hz,Nth is set to be 40 Hz. By doing so, it is possible to know switchingfrom the cooling control mode to the heating control mode in advance.

When the number of revolutions of the compressor 3 is higher than Nth,the target position of the airflow distribution door 16 is set at F/COOL(see FIG. 2) (step S22).

On the contrary, when the number of revolutions of the compressor 3 islower than Nth, it is determined whether or not the airflow distributiondoor 16 is located closer to the F/COOL side than a first specifiedposition. Then, when the airflow distribution door 16 is located closerto the F/COOL side than the first specified position, the control targetposition is defined as the first specified position (step S25).

Here, as shown in FIG. 7, the first specified position is a position atwhich small quantity of adjusting air is distributed into the second airpassage 22. When the airflow distribution door 16 is located at thefirst specified position, smaller quantity of adjusting air flows intothe second air passage 22 than the air flowing into the third airpassage 23. In this state, since both of warm air and cool air are blowninto the room, such control is effective especially when rapid change intemperature of the adjusting air is undesirable, for example, atswitching from heating to cooling.

In this embodiment, since the adjusting air can be passed into thesecond air passage 22 prior to switching from the cooling control modeto the heating control mode, stagnation of high-temperature airgenerating in the vicinity of the second indoor heat exchanger 4 in thecooling operation state can be removed, thereby preventing falsedetection of an air temperature sensor 25.

When the airflow distribution door 16 is not located closer to theF/COOL side than the first specified position at a step S24, an absolutevalue of temperature difference between the blowing temperature and thecontrol target temperature is compared with a predetermined thresholdvalue and it is determined whether or not the blowing temperature ismuch lower than the control target temperature at a step S26.Subsequently, when the blowing temperature is much lower than thecontrol target temperature, the control target position of the airflowdistribution door 16 is shifted toward the F/HOT side (step S27).

At a step S28, for example, an absolute value of temperature differencebetween the blowing temperature and the control target temperature iscompared with a predetermined threshold value and it is determinedwhether or not the blowing temperature is much higher than the controltarget temperature. When the blowing temperature is much higher than thecontrol target temperature, the control target position of the airflowdistribution door 16 is shifted toward the F/COOL side (step S29).Preferably, the shift of the control target position in the steps S27and S29 is performed in increments of the above-mentioned angle.

Such control has an advantage of suppressing rapid change in temperatureof the adjusting air. As described herein, in terms of coolingefficiency, it is especially advantageous that control is carried out soas to reduce the temperature difference only when the temperaturedifference between the blowing temperature and the control targettemperature is large.

The air-conditioning control unit 26 caries out a procedure as shown inFIG. 6 to move the airflow distribution door 16 to the control targetposition thus determined.

That is, at a step S30, the air-conditioning control unit 26 determineswhether or not a time interval T0 has passed since previous positionalcontrol. When T0 has passed, the position of the airflow distributiondoor 16 is controlled and when T0 has not passed, this control isfinished. This prevents the airflow distribution door 16 from movingfrequently, thereby suppressing uncomfortable feeling due to thefrequent operation noise. T0 is set to be one second, for example.

At a step S31, a difference between the control target position and thecurrent position of the airflow distribution door 16 is acquired. Whenthe difference is large, the airflow distribution door 16 is shiftedtoward the determined control target position at a step S32 (DRIVEA/MIX). At this time, it is preferred that the airflow distribution door16 is driven in increments of the above-mentioned angle.

The entire contents of the Japanese Patent Application 2004-104820(filed on Mar. 31, 2004) are incorporated herein by reference,

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments descried above will occur to those skilled in the art, inlight of the above teachings. The scope of the invention is defined withreference to the following claims.

1. An air-conditioning control unit (26) used in an air conditioningsystem (1) which comprises: a refrigerant circuit (2); a first indoorheat exchanger (10) having a low refrigerant temperature; a secondindoor heat exchanger (4) having a high refrigerant temperature;controlled components (5, 12); a first air passage (21); and a secondair passage (22) and a third air passage (23) which are distributed byan airflow distributing door (16) from the first air passage (21),wherein the air-conditioning control unit (26) controls the controlledcomponents (5, 12) and the airflow distributing door (16): wherein thefirst indoor heat exchanger (10) is provided in the first air passage(21); wherein the second indoor heat exchanger (4) is provided in thesecond air passage (22); wherein adjusting air sent from the first airpassage (21) is distributed into the second air passage (22) and the airpassage (23) by controlling the airflow distributing door (16); whereinswitching is carried out between an air flowing state during heating inwhich air is distributed mainly into the second air passage (22) and anair flowing state during cooling in which air is distributed mainly intothe third air passage (23); wherein switching between a coolingoperation state and a heating operation state is carried out bycontrolling the controlled components (5, 12) and thereby performingswitching between a cooling control mode and a heating control mode inthe refrigerant circuit (2); and wherein, in switching from the coolingoperation state to the heating operation state, the flow of theadjusting air in the second air passage (22) is increased by controllingthe airflow distributing door (16) by the air-conditioning control unit(26) prior to the switching of refrigerant circuit from the coolingcontrol mode to the heating control mode.
 2. An air-conditioning controlunit (26) as stated in claim 1, wherein the airflow distributing door(16) is controlled so as to flow smaller quantity of adjusting air intothe second air passage (22) than the air flowing into the third airpassage (23) in the air flowing state during cooling.
 3. Anair-conditioning control unit as stated in claim 1, wherein the airflowdistributing door (16) is controlled so as to flow smaller quantity ofadjusting air into the third air passage (23) than the air flowing intothe second air passage (22) in the air flowing state during heating. 4.An air-conditioning control unit as stated in claim 3, wherein thesecond air passage (22) is connected to an air outlet on the lower sidein the room and the third air passage (23) is connected to an air outleton the upper side in the room.
 5. An air-conditioning control unit asstated in claim 1, wherein position of the airflow distributing door(16) is changed so as to decrease a difference between blowingtemperature of the adjusting air and control target temperature.